Multiple routes to the same destination

[Łukasz Bromirski]

David Gilbert wrote:

> No.  round-robin will deliver packets out-of-order.  TCP will behave
> very badly with this (at the very least, smart selective-ack hosts
> will transmit a lot of selective-ack packets --- but dumb
> non-selective-ack hosts will start asking for a lot of
> retransmission).  Other protocols tolerance for OOO packets varies.

Yeah, but will give You flexibility in doing what You want to do -
for example, sharing two leased lines, 2Mbit/s each. There are
protocols that will behave oddly when they encounter OOB traffic
for TCP (like some BGP implementations for example), but FTP and
others tend generally to accept some low percent of such traffic.

> Linux does all this with it's flow table --- that is each 5-tuple of
> source ip,port dest ip,port (and protocol) is stored as a "flow" in a
> big hash table.  The table stores things like the next-hop interface
> and destination.

Yes, but having an option to do it per-packet or per-flow would be
wonderful. We don't have anything useable today (not counting
static policy-based routing done via ipfw, pf or netgraph). And as
we all know, implementation of flow-based routing can be optimized to
counter DDoS threats - Linux already did that in 2.6.x, as there an
option to compile kernel with either FIB_HASH or FIB_TRIE.

-- 
"Confidence is what you have before you    |            Łukasz Bromirski
  understand the problem." -- Woody Allen   |        lukasz:bromirski,net